1971 LS-6 spark plugs

[Warren F.]

I am having difficulty determining the correct original AC spark plug for the '71 LS-6 application. At Bloomington this year a vendor selling plugs looked it up and said it was R44XLS. Dobbins 1968 to 1972 Stingray Fact Book states it is R44TS. Fellow NCRS member responded with R44.

I'm still unsure, need to know for sure. Thanks

[Mike Cobine]

Re: 1971 LS-6 spark plugs

According to Motors Manual, the R44TS is the correct plug for the 425 hp 454 in 1971. The T means tapered. The S means the tip is extended so it will burn cleaner. A tapered plug does not use a washer. You should be able to look at the hole and see if the seat is tapered or it is flat. After you look at both, you shold be able to tell this easily enough.

The R44XLS is used in the aluminum head of the L88. This si a flat plug that requires a washer. The XL means the threaded section is extended length(long thread area) as needed to grip in the aluminum without stripping the plug hole. The S is again extended tip for cleaner burning.

Personally, I've never noticed a difference with the S or non-S plugs of any type.

You cannot mix the two. Odds are the person assumed you have a regular plug hole and recommended the R44XLS. If you do have a regular plug hole (again, many aluminum heads did), then this is the plug. If you have the tapered seat, then the R44TS is the plug.

Now the bad part. The 44 heat ranges is not available through AC anymore. Only the 43 and the 45. Most sell the R43XLS in the $10-$15 range.

If you need the 44 range for judging, you will end up having to pay the price.

If you need the 44 for driving, you really don't. You can use either the readily available (i.e., normal prices, not absurd restoration, vintage, rare prices) plug you can get from the local parts store.

Hope this helps.

[Mike Cobine]

Re: 1971 LS-6 spark plugs

According to Motors Manual, the R44TS is the correct plug for the 425 hp 454 in 1971. The T means tapered. The S means the tip is extended so it will burn cleaner. A tapered plug does not use a washer. You should be able to look at the hole and see if the seat is tapered or it is flat. After you look at both, you shold be able to tell this easily enough.

The R44XLS is used in the aluminum head of the L88. This si a flat plug that requires a washer. The XL means the threaded section is extended length(long thread area) as needed to grip in the aluminum without stripping the plug hole. The S is again extended tip for cleaner burning.

Personally, I've never noticed a difference with the S or non-S plugs of any type.

You cannot mix the two. Odds are the person assumed you have a regular plug hole and recommended the R44XLS. If you do have a regular plug hole (again, many aluminum heads did), then this is the plug. If you have the tapered seat, then the R44TS is the plug.

Now the bad part. The 44 heat ranges is not available through AC anymore. Only the 43 and the 45. Most sell the R43XLS in the $10-$15 range.

If you need the 44 range for judging, you will end up having to pay the price.

If you need the 44 for driving, you really don't. You can use either the readily available (i.e., normal prices, not absurd restoration, vintage, rare prices) plug you can get from the local parts store.

Hope this helps.

[Warren F.]

Re: 1971 LS-6 spark plugs

Mike:

Thanks for the response. It still seems confusing, because the LS-6 uses the ZL-1 aluminum head (also 2nd design L88 head) and I would have thought it needed the extended thread length as well. However since it is 3 compression points lower (12 to 1 vs 9 to 1), it probably would not be the same heat range.

[Warren F.]

Re: 1971 LS-6 spark plugs

Mike:

Thanks for the response. It still seems confusing, because the LS-6 uses the ZL-1 aluminum head (also 2nd design L88 head) and I would have thought it needed the extended thread length as well. However since it is 3 compression points lower (12 to 1 vs 9 to 1), it probably would not be the same heat range.

[Mike Cobine]

Re: 1971 LS-6 spark plugs

I would think it would be the same, also. However, you have to check the head. If the hole is for a tapered plug, you will see. Take any tapered plug (R45T, R44TS, etc.) and insert it by hand, watching carefully if the plug seats against the seat of the hole. As the plug gets close, you will see if it is fitting or if it is wrong.

You can also try any non-tapered plug (44, R44, 45, etc.) and insert by hand to see if it seats correctly or not.

[Mike Cobine]

Re: 1971 LS-6 spark plugs

I would think it would be the same, also. However, you have to check the head. If the hole is for a tapered plug, you will see. Take any tapered plug (R45T, R44TS, etc.) and insert it by hand, watching carefully if the plug seats against the seat of the hole. As the plug gets close, you will see if it is fitting or if it is wrong.

You can also try any non-tapered plug (44, R44, 45, etc.) and insert by hand to see if it seats correctly or not.

[Terry M.]

[Terry M.]

[Clem Z.]

Re: 1971 LS-6 spark plugs

all BBC ALUMINUM heads take the 3/4" reach R45 XLS plugs. the cast iron heads take the tapered seat plugs after 1970

[Clem Z.]

Re: 1971 LS-6 spark plugs

all BBC ALUMINUM heads take the 3/4" reach R45 XLS plugs. the cast iron heads take the tapered seat plugs after 1970

[Michael W.]

Re: 1971 LS-6 spark plugs

Clem, I'm surprsed at you. You actually used capitalisation in your post! What's going on, you developing the same capslock problem as Jerry?

[Michael W.]

Re: 1971 LS-6 spark plugs

Clem, I'm surprsed at you. You actually used capitalisation in your post! What's going on, you developing the same capslock problem as Jerry?

[Clem Z.]

Re: 1971 LS-6 spark plugs

the caps are so the reader does not miss the important words.

[Clem Z.]

Re: 1971 LS-6 spark plugs

the caps are so the reader does not miss the important words.